This miniature portrait is signed "Florence Mackubin after Chartran". Florence Mackubin (1866-1918) worked in several different cities. See Annapolis Collection - Florence Mackubin for some examples of her large portraits.
She had studied art in Fontainebleau, in Munich, and in Paris. She was commissioned by the State of Maryland to copy the portrait of Queen Henrietta Maria, for whom Maryland was named and her copy now hangs in the Annapolis State House. There are numerous Internet references to her work.
MacKubin specialized in portraits (miniatures, pastels, and oil) of governors, government officials, and socially prominent women. At the 1893 Exposition, she exhibited 58 pastels and won a Bronze Medal. She also visited Europe on several occasions and her return is noted in New York arrival records dated; 21 Jun 1876, 22 Jun 1891, 12 Dec 1892, and 21 Nov 1903. The 1910/1911 Who's Who stated she was born in Florence, Italy of American parents and in 1911 was living in Canada ar St Andrews, New Brunswick.
The reference to Chartran, is to Theobold Chartran (1849-1907) who was a noted French portrait painter of the period. Chartran visited the United States on several occasions, as shown in New York arrival records dated 14 Nov 1896, 18 Jan 1904, and 15 Jan 1906. It is probable these visits were to undertake painting commissions. For more about him, see Theobald Chartran - Wikipedia, the free encyclopedia
At the time, it was not uncommon for the owner of a large portrait to commission a miniature copy of it. This is most likely the case here, but the whereabouts of the large portrait and the name of the sitter are both unknown. 680